Learning C recently, I ran into confusion around FLT_EVAL_METHOD as my dirty (not recommended) trick for getting machine epsilon didn't work (7.0/3.0 - 4.0/3.0

Learning C recently, I ran into confusion around FLT_EVAL_METHOD as my dirty (not recommended) trick for getting machine epsilon didn't work (7.0/3.0 - 4.0/3.0 - 1.0). With strict IEEE 754 floating points it works fine (Python, Julia, Go all work as expected). But gcc, with c11 flags at least, performed the computation using the 80 bit upsampling mentioned in this post. Caused some head-scratching initially. Edit: Also, curiously, things worked as expected for me using -std=gnu11. This was a fairly old version of GCC though, things might have changed.